Destructive and nondestructive analysis of some elements in tissue and environmental samples by thermal neutron activation analysis technique

A rapid and selective method has been developed and applied for determining elements present in tissue and environmental samples by both destructive and nondestructive activation analysis. Nondestructive activation analysis involves the irradiation of the sample and standard of the elements such as Mn, Na, and K with thermal neutrons from²⁵²Cf neutron source followed by radioassay of the (n,r) products on a HPGe detector coupled to a PC-based MCA. Elements are determined by irradiating the samples in the thermal neutron flux of the CIRUS reactor and radiochemically separating the isotopes of interest using substoichiometric extraction and precipitation technique. The statistical evaluation of the method with respect to accuracy and precision of the method and its sensitivity are discussed.     

Biomedical neutron research at the Californium User Facility for Neutron Science

The Californium User Facility for Neutron Science has been established at Oak Ridge National Laboratory (ORNL). The Californium Use Facility (CUF) is a part of the larger Californium Facility, which fabricates and stores compact²⁵²Cf neutron sources for worldwide distribution. The CUF can provide a cost-effective option for research with²⁵²Cf sources. Three projects at the CUF that demonstrate the versatility of²⁵²Cf for biological and biomedical neutron-based research are described: future establishment of a²⁵²Cf-based neutron activation analysis system, ongoing work to produce miniature high-intensity, remotely afterloaded²⁵²Cf sources for tumors therapy, and a recent experiment that irradiated living human lung cancer cells impregnated with experimental boron compounds to test their effectiveness for boron neutron capture therapy.     

Precise simultaneous determination of zirconium and hafnium in silicate rocks,meteorites and lunar samples

A precise, sensitive and rapid analytical technique has been developed for the simultaneous determination of Zr and Hf in natural silicate matrices. The technique is based on radiochemical neutron activation analysis and employs a rapid fusion dissolution of the sample and simultaneous precipitation of the Zr−Hf pair with p-hydroxybenzene arsonic acid in an acidic medium. The indicator radionuclides,⁹⁵Zr and¹⁸¹Hf, are counted with a pair of high resolution Ge(Li) detectors and the⁹⁵Zr activity is corrected for the contribution from U fission. The chemical yields of the radiochemical separation are based on Hf carrier, which quantitatively carries both Zr and Hf. The yield is determined by reactivation of the processed samples and standards with a²⁵²Cf isotopic neutron source and by counting the 18.6 sec half-life^179mHf. The sensitivity, precision and accuracy of the procedure are demonstrated by replicate analyses of several standard rocks, meteorites and lunar samples which exhibit a wide range of Zr and Hf abundances.     

The application of NAA with irradiation at reduced temperature for the study of element losses during pretreatment of biological samples

The neutron capture gamma-ray spectroscopy facility assembled at the Institute of Radiochemistry, KfK (for analytical purposes) using a²⁵²Cf neutron source with a strength of 6·10⁷ n/s, has been used to check its applicability and sensitivity for quantitative analyses of ores. The analysis of Sm, Cd and Mn in phosphate and monazite rock samples has been carried out. The results from this study show a variation of about 25% from the values determined by RNAA method. This discrepancy could be mainly due to the low signal-to-background ratio observed which is caused by (i) scattering of the source gammarays by the target, and (ii) interference from the 2223.1 keV neutron capture hydrogen gamma-rays produced by the moderated materials and from their compton scattering in the detector. To overcome these difficulties we suggest to introduce a 2.5 cm thick polyethylene sheet between the detector⁶Li-cap shielding and the target as well as to increase the detection solid angle. Also the strength of the²⁵²Cf neutron source should be increased by an order of magnitude and the neutron beam should be collimated to obtain the optimal thermal neutron flux with a low level of²⁵²Cf gamma-rays. This can be achieved by setting up between the neutron source and the target a conical polyethylene collimator with a thickness of 10 cm containing a 1 cm thick lead sheet.     

The application of a252Cf neutron multiplier for routine instrumental neutron activation analysis

The successful application of instrumental neutron activation analysis for routine determinations depends on the ability to produce accurate and precise analytical results in a relatively short time. An important factor in obtaining the desired speed has been the availability of a low-cost, moderate-flux neutron source for on-site use. The²⁵²Cf neutron multiplier (CFX), designed and constructed by Intelcom Rad Tech Corporation of San Diego, California, is a subcritical assembly capable of continuous, stable operation and has provided us with the ability to determine more than 35 elements as major and minor components. The CFX produces a thermal neutron flux of ∼2×10³ n/cm²-sec by a 100-fold multiplication of the neutrons emitted from a 1 mg²⁵²Cf source. Of particular importance in its application at Kodak has been the determination of the halogens Cl, Br, and I, both singly and simultaneously, in various matrices including photographic materials.     

Determination of Macro, Micro and Ultra Micro Concentration of Some Elements in Normal and Diseased Tissues of the Bone by NAA Employing 252Cf and Reactor Neutrons

A method has been developed for the determination of elements in normal and diseased tissues of the bone employing radiochemical and instrumental neutron activation analysis. Elements such as Na, Br, Au, Sb, Sc, Fe, Zn and Cr were subjected to irradiation in ²⁵²Cf or CIRUS reactor followed by measurement of the activity on a HPGe detector coupled to a PC based MCA unit. Elements such as Co, Ca and P were subjected to radiochemical separation prior to the measurement. The statistical evaluation with respect to accuracy and precision is discussed.     

Experimental Evaluation of a Portable Neutron-Based Gamma-Spectroscopy System for Chloride Measurements in Reinforced Concrete

A portable prompt gamma neutron activation (PGNA) spectroscopy system has been developed to analyze the elemental composition (Ca, Si, Al, etc.) of reinforced concrete and to measure chloride contamination. The portable PGNA system consists of a high purity germanium (HPGe) gamma detector with a 70% relative efficiency, a ²⁵²Cf neutron source and moderator subsystem, and a portable multichannel analyzer system integrated with a laptop computer. Two types of activation experiments were performed to evaluate the device: first, a detector calibration using a Cl gamma standard provided by a PGNA facility; second, an evaluation of the actual performance of the complete system with the ²⁵²Cf source using full scale test slabs containing known amounts of chloride. Both methods indicate that it is feasible to use this device to measure the chloride content of reinforced concrete in the field. The chloride level for the corrosion threshold can be measured with a precision of 10% for a counting time of roughly 6 minutes. This makes the PGNA method competitive with the conventional destructive method.     

Instrumental neutron activation analysis of some ancient punchmark coins from India

A nondestructive instrumental neutron activation analysis technique is applied for the analysis of precious ancient punchmark coins. Coins ranging between 8th century B.C. to 2nd century B.C. were irradiated with thermal neutrons in a²⁵²Cf neutron source facility and analyzed by comparator method of instrumental neutron activation analysis, using high purity germanium detector coupled to a multichannel analyzer, the activities being measured at photopeak energies of the corresponding radioisotopes. It is observed that punchmark coins are mainly of two types: copper or silver based. Other elements present in varying proportions are gold, arsenic and antimony.     

The use of threshold energy differences in fast neutron activation analysis for oxygen and fluorine

A method is described for the simultaneous determination of oxygen and fluorine; the latter has a lower neutron-activation threshold energy so that the fluorine-to-oxygen¹⁶N formation ratio changes after partial moderation of the incident 14.7 MeV neutron beam. In mixtures containing approximately equal amounts of fluorine and oxygen, these elements can each be determined with a precision of ca. ±1%; as expected, errors in the determination of a minor component (ca. 17%) are larger, being ca. ±5%.     

The neutron flux of a252Cf neutron activation analysis device using the MCNP code

This report presents results from the application of the Monte Carlo N-Particle (MCNP) computer code to the²⁵²Cf neutron activation analysis (NAA) Device in the Technical Physics Institute of the Heilongjiang Science Academy of the People's Republic of China. The thermal and epithermal neutron flux at the sample positions and the neutron and photon fluxes on the surfaces of the device were calculated. A comparison between the calculated and experimental thermal and epithermal neutron fluxes at sample positions yield relative errors of less than 10% for the thermal neutron flux.     

Neutron energy spectra of 252Cf, Am-Be source and of the D(d,n)3He reaction

The neutron energy spectrum of the following sources were measured using a fast neutron spectrometer with the NE-213 liquid scintillator: ²⁵²Cf, Am-Be and D(d,n)³He reaction from a 3 MeV Pelletron accelerator in Tokyo Institute of Technology. The measured proton recoil pulse height data of ²⁵²Cf, Am-Be and D(d,n)³He were unfolded using the mathematical program to obtain the neutron energy spectrum. The ²⁵²Cf and Am-Be neutron energy spectra were measured and the results obtained showed a good agreement with the spectra usually published in the literature. The neutron energy spectrum from D(d,n)³He was measured and the results obtained also showed a good agreement with the calculation by time of flight (TOF) methods.     

Fabrication of 50-mg252Cf neutron sources for the FDA activation analysis facility

The Transuranium Processing Plant (TPP) at the Oak Ridge National Laboratory (ORNL) has been requested by the Food and Drug Administration (FDA) to furnish 200 mg of²⁵²Cf for use in their new activation analysis facility. This paper discusses the procedure to be employed in fabricating the californium into four neutron sources, each containing a nominal 50-mg of²⁵²Cf. The completed neutron sources will be assayed using a precision fast-neutron counter, decontaminated and loaded into a concreete-shielded shipping container weighing 10.7 Mg for shipment to the FDA facility located at Howard University in Washington, D. C.Research sponsored by the Office of Basic Energy Sciences, U. S. Department of Energy, under contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.     

Eine 3mg-252Cf-Bestrahlungsanordnung-Aufbau und Anwendungen

In the last years Cf-252 neutron sources will be incresingly used for nuclear analytical purposes. In the Central Institute of Isotope and Radiation Research, Leipzig, an irradiation equipment with a 3mg²⁵²Cf neutron source was constructed. It reaches thermal neutron fluxes of about 10⁷ n·cm^–2·s^–1. The construction of this equipment and the different moderation geometries are described. Possibilities of the application for neutron induced autoradiography, neutron radiography and neutron activation analysis are demonstrated on examples.     

A method for bulk hydrogen analysis based on transmission and back scattering of fast neutrons

A method was proposed for bulk hydrogen analysis. It is based on simultaneous detection of transmitted fast neutrons and back scattered thermal neutrons from the investigated samples by ³He detectors. The fast neutron beams were obtained from ²⁵²Cf and Pu–Be neutron sources. The experimental set-up as well as samples preparation were described. Incident thermal neutrons beams obtained from either ²⁵²Cf or Pu–Be sources, were used to investigate the samples by neutron backscattering. The results obtained from transmission and backscattering of fast neutrons were compared and discussed. The advantage and capabilities of the proposed method were presented. The results obtained using fast neutron beams are more sensitive than those obtained using thermal neutron beams. Validation procedures were proposed to credit the results.     

In vivo measurement of the Ca/P ratio by local activation with isotopic neutron sources

In connection with the study and the treatment of generalised demineralising bone diseases, the amount of phosphorus and calcium has been determined in the hand by “in vivo” neutron activation analysis using²⁵²Cf and²³⁸Pu−Be isotopic neutron sources. The statistical accuracy of the induced radioactivity measurement carried out on the hand of a normal subject is about 2% for P and Ca, while the standard deviation over a series of 10 analyses performed on a same phantom remains within 3% for both P and Ca. The results are normalized and expressed in grams of P or Ca per cm³ of bone. The values observed on a group of 55 normal subjects and on some osteoporotic patients are given.     

The comparison of four neutron sources for Prompt Gamma Neutron Activation Analysis (PGNAA) in vivo detections of boron

A Prompt Gamma Ray Neutron Activation Analysis (PGNAA) system, incorporating an isotopic neutron source has been simulated using the MCNPX Monte Carlo code. In order to improve the signal to noise ratio different collimators and a filter were placed between the neutron source and the object. The effect of the positioning of the neutron beam and the detector relative to the object has been studied. In this work the optimisation procedure is demonstrated for boron. Monte Carlo calculations were carried out to compare the performance of the proposed PGNAA system using four different neutron sources (²⁴¹Am/Be, ²⁵²Cf, ²⁴¹Am/B, and DT neutron generator). Among the different systems the ²⁵²Cf neutron based PGNAA system has the best performance.     

Analyse par activation et numismatique

In this communication we show that two nuclear methods permit a non-destructive determination of major, minor and trace elements in three important “archaeological” metals: gold, silver, copper and alloys. With the first one, neutron activation analysis with a²⁵²Cf neutron source, we can perform a fast and accurate determination of three important elements of the coin's composition, viz. gold, silver and copper. With the second one, proton activation analysis, we can determine trace elements at ppm level in gold, silver and copper metals. Using these two techniques of activation analysis two important numismatic problems can be studied: the evolution of the fineness; characterization or differentiation by the trace elements the metal used to mint the coin. One example of each numismatic problem is also given.      

Determination of the silver content of ancient silver coins by neutron activation analysis

A reactor neutron activation analysis procedure for the determination of the silver content of silver coins is described. The samples are irradiated for 1 s, cooled for 85 s and measured for 60 s with a Ge-detector. The analysis is based on the measurement of¹¹⁰Ag and¹⁰⁸Ag. Aluminium is used for flux monitoring and pulse pile-up correction. A calibration curve is prepared by irradiating and measureing a series of discs with known silver contents. An average precision of ±2.1% is obtained. The analysis of coins with known silver contents shows good agreement with the given values. The analysis time is 2.5 minutes per sample.     

Einsatz Verschiedener Neutronenquellen zur Analytischen Nutzung Prompter Neutroneneinfanggammastrahlung

The analytical use of the prompt gamma-rays originating from neutron capture is a valuable completition of the conventional neutron activation analysis. The application of the external radiation tube P2 of the research reactor in Munich, an Am—Be neutron source of 300 mCi and a 1 mg²⁵²Cf neutron source is discussed.